DNS Check
WARN Glue at parent nameservers
WARNING. The parent servers (I checked with ns-ext.isc.org.) are not providing glue for all your nameservers. This means that they are supplying the NS records (host.example.com), but not supplying the A records (192.0.2.53), which can cause slightly slower connections, and may cause incompatibilities with some non-RFC-compliant programs. This is perfectly acceptable behavior per the RFCs. This will usually occur if your DNS servers are not in the same TLD as your domain (for example, a DNS server of "ns1.example.org" for the domain "example.com"). In this case, you can speed up the connections slightly by having NS records that are in the same TLD as your domain.
WARNING: We cannot test to see if your nameservers are all on the same Class C (technically, /24) range, because the root servers are not sending glue.